This invention relates to an apparatus and process for separating gas-liquid mixtures. More particular, this invention is directed to an improved means of disengaging gas from a gas-liquid mixture at the top of a vertical, upflow reactor or tube in which the liquid overflow from the tube or reactor is modified by directing the liquid flow through a series of alternating riser and downcomer compartments placed at the top of the upflow reactor or tube.
Systems for separation of heterogeneous mixtures containing components of different densities-- i.e. a gas dispersed in a denser, continuous liquid phase-- by decantation in a dynamic or upflow apparatus are known, For example, Netherlands Pat. No. 7,512,807 describes a separation apparatus comprising a central, cylindrical upflow tube or bubble column which opens at its top, via an overflow edge, into a separator hood fitted over and around the top of the upflow tube, said separator hood having a gas outlet above the overflow edge and a liquid outlet below the overflow edge and outside the upflow tube. With the separation apparatus of this Netherlands patent, the top circumference of the upflow tube itself as the liquid overflow edge; liquid flowing directly from the upflow tube over the uppper surface of the upflow tube into the annulus formed by the lower portion of the separator hood for collection and subsequent removal via the liquid outlet.
It has now been determined that the degree to which a separation between gas and liquid is effected by means of the above-mentioned apparatus depends on the combined effect of a residence of the phases to be separated in the separator hood and of the movement of the phases over the overflow edge. In certain applications it has been found, when using the above-mentioned simplest embodiment of the separating device, that the effect of the circular overflow edge alone does not bring about an adequate separation. One such application where inadequate separation is obtained is the synthesis of hydrocarbons from synthesis gas in a slurry type reactor in which the catalyst is suspended in recycled liquid product or in a circulating auxiliary liquid and wherein the liquid and catalyst, after having been separated from unconverted gas and gaseous by-products at the top of the upflow reactor, are cooled outside the reactor and recycled to the bottom of the reactor. In cases such as this, the separation then has to be completed in the space of the separator hood outside the upflow tube where, below the overflow edge, a liquid level must be maintained with a very large surface area. This, in turn, calls for an outer diameter of the separator hood many times larger than that of the upflow tube or reactor which is unacceptable in practice.
The present invention provides a solution to this problem of inadequate separation of phases while at the same time avoiding the disadvantages attributable to the need for a large liquid surface area in the separator hood of the prior art gas-liquid separation apparatus.